1. Field of the Invention
The invention relates to vehicle bodies, particularly semi-trailers constructed in a semi-monococque structure with stressed plates joined with top and bottom rails and external vertical bracing through external side posts or vertical supports thereby achieving improved strength to weight ratio and maximizing internal cubic capacity.
2. Description of the Prior Art
Various methods of construction of semi-trailer side walls have been used. Typically side wall panels are continuous and stiffened by internal or external vertical side posts (see e.g., Glassmeyer U.S. Pat. No. 3,815,500). Placement of structural side posts or "stakes" with the space therebetween filled by panels is shown in Glassmeyer U.S. Pat. No. 4,042,275. The use of side posts as major structural members has a major disadvantage in that the thickness of the structural posts detracts from available volume or cubic capacity within the semi-trailer either by displacing the wall inward from the maximum width of the trailer, fixed by law or administrative regulation in most jurisdictions, or by the protrusion of internal side post into the cargo area. Both alternatives effectively limit the width available internally for typical packaged or non-bulk cargo, and thereore the cubic capacity.
Accordingly various efforts have been made to utilize a stronger wall element, in particular aluminum plate, while using side posts of minimal thickness thereby maximizing internal volume or cubic capacity for a given strength and weight and given regulatory width limitations. Examples of these include Banerjea, U.S. Pat. No. 4,685,721 and Ehrlich, U.S. Pat. No. 4,810,027.
Banerjea uses vertical joining panels in order to interconnect a series of plates. Joining panels are used rather than side posts or support members because varying thickness plates are utilized to optimize shear strength in selected portions of the vehicle, as near the fifth wheel king pin, landing gear and rear bogies or rear suspension assembly. By comparison, the instant invention uses a refined geometry for the side post itself, integrally utilizing top and bottom rails providing an improved unitary structure.
Ehrlich U.S. Pat. No. 4,810,027 specifically addresses a structure which in section utilizes a side post, a side lap and butted side plates. The disclosure is limited to the use of the side lap element both to form a box-like structure and to seal gaps created by the specific geometry used in the Ehrlich top rail, side post assembly and bottom rail structure. The instant invention uses improved geometry to dispense with the side lap, yet the unitary structure provides an appropriate strength and operatively sealed structure.
Other prior art tending to show frameless or monococque vehicle body or semi-trailer construction includes Schmidt, U.S. Pat. No. 4,212,405 which uses thick plate including internal posts or stiffeners and limiting to certain stock dimensions and standard alloys. Curell U.S. Pat. No. 2,901,283 utilizes external side posts with a series of elongated diagonal members forming substantially open or perforated side walls.